Adjustable hand held pipettes have been widely used in liquid handling systems, e.g., U.S. Pat. Nos. 4,263,257 to Metsala and 4,268,481 to Suovaniemi, et al. While hand held pipettes currently in use provide precise volume adjustment and accurate volume read out, such pipettes provide volume adjustment control setters which move axially with the pipettes plunger action and which, therefore, must be adjusted while in constant motion.
Currently used seal assemblies used in hand pipettes of the type herein involved typically comprise TEFLON (a trademark of E. I. Dupont de Nemours) seal assemblies which tend to wear out at unnoticeable rates. This introduces non-reproducible errors in the transferred volume and such seal assemblies therefore include undesirable qualities.
Thus, currently used hand held pipettes have several disadvantages. In the first place, most of these adjustable pipettes use TEFLON seals that lose their sealing capability after extended use. Secondly, these pipettes are very difficult to adjust to the desired volume when the user is wearing gloves, necessary when working with radioactive or biohazardous materials. Thirdly, most of the adjustable pipettes currently in use are not autoclavable. This tends to increase the risk of bacterial contamination or infection by pathogenic organisms contained in transferred liquids. A fourth disadvantage of the most widely used adjustable pipettes is that they are not designed to provide accessible servicing and thereby save the user time and money.